如何编写getatrribute，以便可以返回dict中的变量？

Question

我有一堂课，里面有一个字典。我想通过直接“ instance.key”而不是“ instance.d [key]”来访问字典中的变量。怎么做？

class A:
    def __init__(self):
        self.a = 1
        self.b = 2
        self.fields = {'c': 3, 'd': 4}


def main():
    a = A()
    print(a.a) # 1
    print(a.b) # 2
    print(a.c) # currently raise Exception, I want it to print 3
    print(a.d) # currently raise Exception, I want it to print 4


if __name__ == '__main__':
    main()

Answer 1

您可以覆盖object.__getattr__(self, name)方法（可以定义此类方法以自定义类实例的属性访问的含义）：

class A:
    def __init__(self):
        self.a = 1
        self.b = 2
        self.fields = {'c': 3, 'd': 4}

    def __getattr__(self, item):
        return self.__dict__.get(item) or self.__dict__['fields'].get(item)

a = A()
print(a.a) # 1
print(a.b) # 2
print(a.c) # 3
print(a.d) # 4

推荐链接： __getattr__